As the cable industry moves from hybrid fiber coax (“HFC”) to IP based fiber (EPON or GPON), it is preferable to do this in steps to reduce capital expenditures. An incremental step for this is using a technology called Radio Frequency over Glass (“RFOG”). RFOG delivers the same or better performance as coax with reduced noise susceptibility and increased usable RF spectrum in both the downstream and upstream directions. RFOG also allows service providers to continue to leverage traditional HFC equipment and back-office applications as well as installed CPE (customer premise equipment). Cable operators can continue to rely on the existing provision and billing systems, Cable Modem Termination System (CMTS) platforms, headend equipment, set-top boxes, and cable modems while gaining benefits inherent with RFOG.
In RFOG, the coax portion of a cable system is replaced with fiber from the headend to a subscriber's home or other premises. However, the subscriber's premises retains its coax cable and all of the equipment in the home is unaware of the coax to fiber conversion outside. For example, as shown in FIG. 1, an RFOG system 10 has a head end 12 that transmits and receives signals from a subscriber's premises 14 via fiber optic cables 16. As in an HFC system, the subscriber's premises 14 includes coax cables 18 connected to the equipment 20 such as televisions, set-top boxes, and so forth, which are unaware of the fiber optic cables 16.
The RFOG system 10 includes a transmitter 22 and a receiver 24 at the headend 12 that converts all of the RF signals to/from a modulated laser wavelength. An Optical Node Unit (“ONU”) 26 located at, for example, the subscriber's premises 14, is used to convert this laser wavelength to RF/coax signals for use in the coax cables 18 and the equipment 20.